house of cards vs cardcastle

house of cards and cardcastle both are nouns.

Word	Noun	Adjective	Verb	Adverb
house of cards	Yes	No	No	No
cardcastle	Yes	No	No	No

As nouns, house of cards and cardcastle are synonyms defined as:

house of cards and cardcastle: an unstable construction with playing cards

Other synonyms of house of cards include card-house, cardhouse.

house of cards (noun)	cardcastle (noun)
an unstable construction with playing cards	an unstable construction with playing cards
a speculative scheme that depends on unstable factors that the planner cannot control